Abstract:

Objective ·To investigate the effects of nitrogen dioxide (NO₂) exposure timing and concentration on vascular endothelial dysfunction (VED) in elderly individuals using flow-mediated dilation (FMD) technology. Methods ·A cross-sectional study was conducted among elderly participants who underwent FMD testing at Tongren Hospital, Shanghai Jiao Tong University School of Medicine, between 2020 and 2022. All participants completed detailed questionnaires and clinical examinations, including demographic characteristics, lifestyle factors, and medical history. Individual NO₂ exposure levels were obtained by matching residential addresses with pollution data grids from the Tracking Air Pollution in China (TAP) platform. Generalized additive models combined with distributed lag non-linear models (DLNM) were employed to analyze the impact of NO₂ on FMD and VED, with adjustments for meteorological factors, individual characteristics, and health status as potential confounders. Results ·A total of 812 eligible participants were included after rigorous screening. The results demonstrated that NO₂ exposure was significantly associated with decreased FMD at lag days 1, 2, and 5 (P=0.003, P=0.034, P=0.022), while the risk of VED increased significantly at lag days 5 and 6. Cumulative effect analysis revealed a significant dose-response relationship between NO₂ concentrations (35‒85 μg/m³) and FMD reduction (P<0.05). Subgroup analysis indicated that participants without dyslipidemia or a history of coronary artery disease (CAD) were more susceptible to short-term NO₂ exposure. Conclusion ·This study systematically revealed, for the first time, that short-term NO₂ exposure has a negative impact on vascular endothelial function in elderly individuals, exhibiting distinct temporal patterns and concentration thresholds. NO₂ exposure within 1‒6 d significantly impaired endothelial function, with the most pronounced effects observed on day 5. Notably, clinically "healthy" elderly individuals (without hyperlipidemia or CAD) demonstrated higher susceptibility. These findings not only support the critical role of NO₂ in vascular endothelial injury but also provide important evidence for elucidating the mechanisms by which air pollutants contribute to cardiovascular diseases through vascular dysfunction. The study holds significant implications for developing targeted air pollution prevention strategies for the elderly population.

Key words: nitrogen dioxide, endothelial function, flow-mediated dilation, vascular endothelial dysfunction